This disclosure relates to steer-by-wire vehicle control systems.
Steering equipment for assisting a driver to steer an automobile is well known in the art. In conventional steering assemblies, the operator controls the direction of the vehicle with the aid of a steering wheel. This wheel is mechanically connected, usually through a gear assembly to the road wheels. To aid the operator, many systems utilize an auxiliary system to generate a force that is transmitted to a steering gear assembly. The additional force reduces the effort required by the operator in changing the direction of the vehicle. Typically, this auxiliary force is generated by either a hydraulic drive or an electric motor.
Because the steering wheel is connected directly to the road wheels, the resulting mechanical assembly that provides the connection can be quite complicated and expensive to produce. The one advantage in having a direct connection is that the operator receives tactile feedback through the steering wheel. For example, if the vehicle changes directions while it is moving, the operator will feel resistance in the steering wheel.
Therefore, is it considered advantageous to provide a steering control system that is less expensive than a traditional mechanical system while still providing the tactile feedback to the operator.
The present invention is directed to a control system and method, which provides a vehicle operator with an electronic steering or steer-by-wire control for a vehicle. The steer-by-wire control system comprises a road wheel unit and a steering wheel unit that operate together to provide steering control for the vehicle operator. A master control unit may be employed to support performing the desired signal processing. Signals from sensors in the road wheel unit, steering wheel unit, and vehicle speed are used to calculate road wheel command signals to control the direction of the vehicle and steering wheel torque commands to provide tactile feedback to the vehicle operator. An Ackerman correction may be employed to adjust the left and right road wheel angles correcting for errors in the steering geometry to ensure that the wheels will track about a common turn center.